<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
		<select id="country-select">
			<option value="china">中国</option>
			<option value="use">美国</option>
			<option value="japan">日本</option>

		</select>
		<select id="city_select">
			<option value="">请选择一个城市</option>
		</select>
		<script type="text/javascript">
			var countries={
				'china':['北京','上海','广州'],
				'use':['纽约','洛杉矶','华盛顿'],
				'japan':['东京','大板','长崎']
			};
			document.getElementById('country-select').addEventListener('change',function(){
				var citySelect = document.getElementById('city_select');
			})
		</script>
	</body>
</html>
